Using non-prescipitating monospecific antibodies we have been studying the conformations of hemoglobins in solution. Hemoglobin A0 and A2 have been isolated, purified and isotopically labeled either by carbamoylation with K14 CNO or by reductive alkylation with tritiated borohydride. A specific subpopulation of anti-hemoglobin antibodies has been isolated by affinity chromatography using a synthetic peptide corresponding to alpha (129-141) and has been used in a radio-immunoassay to study conformational changes that occur at the carboxy-terminus of alpha chains during oxygenation. These antibodies which bind with an affinity of 5 x 10 to the 8th power M to the negative 1st power to CO-liganded 14(C) hemoglobin increase the oxygen affinity of hemoglobin and, thus, act as a linked function. A second subpopulation of antibodies has been isolated that react specifically with 3 (H)-hemoglobin A2. These antibodies will be used in a radioimmunoassay to detect hemoglobin A2 levels in serum and cultured erythropoietic cells as well as to differentiate A2 from other normal and mutant hemoglobins.